Unsaturated monomers, polymers, chemically amplified resist composition, and process of pattern formation

ABSTRACT

There is provided a chemically-amplified resist composition having high transparency to light having a wavelength of 220 nanometers or smaller, excellent resistance to etching, and excellent adhesion to a substrate. The chemically-amplified resist composition is prepared through the use of at least one of a repeated structural unit having a bridged alicyclic γ-lactone structure defined in the general formula (III), a repeated structural unit having a bridged alicyclic γ-lactone structure defined in the general formula (IV), and a repeated structural unit having a bridged alicyclic γ-lactone structure defined in the general formula (V).

BACKGROUND OF THE INVENTION

[0001] The invention relates to a polymer including a novel bridgedalicyclic γ-lactone structure, and more particularly to a polymersuitable for a chemically-amplified resist composition to be exposed tofar ultra-violet rays having a wavelength of 220 nanometers or smaller.The invention relates further to an unsaturated monomer useful as rawmaterial monomer of which the polymer is composed, achemically-amplified resist composition containing the polymer, and amethod of forming a pattern.

PRIOR ART

[0002] In a field of manufacturing various electronic devices such as asemiconductor device in which half-micron order patterns are required toform, an electric device is now required to have higher densificationand integration. Thus, an improved lithography technique for forming aminuter pattern on a substrate is required for satisfying such arequirement.

[0003] In particular, photolithography employing an ArF excimer laser(193 nm) has been suggested for manufacturing a DRAM having anintegration of 1 Gbit or higher which is necessary to form a pattern of0.13 micrometers or smaller, for instance, in Donald C. Hofer et al.,“193 nm Photoresist R&D: The Risk & Challenge”, Journal of PhotopolymerScience and Technology Vol. 9, No. 3 (1996), pp. 387-397.

[0004] Hence, there is now expected to develop a new resist to beemployed for photolithography in which ArF excimer laser is to be used.

[0005] Such a resist to be exposed to ArF laser beams is required toenhance cost performance of laser beams, because a gas from which laserbeams are radiated has short lifetime, and further because an equipmentfor radiating laser-beams is expensive. Thus, the resist is expected tohave high sensitivity as well as a high resolution in response to adesign rule getting smaller and smaller.

[0006] For instance, Japanese Patent Application Publication No.59-45439 has suggested, as a chemically-amplified resist, a resistcomposition containing poly(p-tert-butoxycarbonyloxy-α-methylstyrene)and triphenylsulfonium.hexafluoroacenato. Such a chemically-amplifiedresist is employed broadly for a KrF excimer laser, for instance, assuggested in American Chemical Society Symposium Series, 1984, Vol. 242,pages 11-23, reported by Hiroshi Ito and C. Grant Willson.

[0007] A chemically-amplified resist is characterized by that protonacid is generated when a photo acid generator contained therein isexposed to light, and the thus generated proton acid causes acidcatalyst reaction with a resist resin when the proton acid is headedafter the exposure thereof to light. Thus, a chemically-amplified resistcan have quite higher sensitivity in comparison with a prior resistwhich has an optical reaction efficiency, defined as reaction per aphoton, of smaller than one (1). Presently, most of newly developedresists are chemically amplified resists.

[0008] In lithography in which light beams having a wavelength equal toor smaller than 220 nanometers, such as ArF excimer laser beams, areused, a resist is required to have high transparency to light having awavelength equal to or smaller than 220 nanometers, and resistance todry etching.

[0009] Photoresists used for g-line having a wavelength of 438 nm,i-line having a wavelength of 365 nm or KrF excimer laser having awavelength of 248 nm are composed of resins including aromatic rings ina unit structure, such as novolak resin or poly (p-vinylphenol). A dryetching resistance of such aromatic rings gives an etching resistance tothe resins.

[0010] However, a resin including aromatic rings quite intensivelyabsorbs light having a wavelength equal to or shorter than 220nanometers. Hence, if a photoresist composed of a resin includingaromatic rings therein is used in a photolithography in which lightbeams having a wavelength equal to or shorter than 220 nanometers suchas KrF excimer laser beams (193 nm) are used, most of the light beams isabsorbed at a surface of the resist, and accordingly, cannot reach asubstrate with the result that a minute resist pattern cannot be formed.

[0011] Accordingly, it is quite difficult to apply a resin includingpresently used aromatic rings to a photolithography in which lighthaving a wavelength equal to or shorter than 220 nanometers is used.Thus, there is a need for a resist which does not include aromatic ringstherein, which is transparent to light having a wavelength equal to orsmaller than 220 nanometers, and which has resistance to etching.

[0012] As a polymer having transparency to ArF excimer laser beamshaving a wavelength of 193 nanometers and further having resistance todry-etching, there have been suggested a copolymer havingadamantylmethacrylate units which are alicyclic polymer, in Takechi etal., Journal of Photopolymer Science and Technology, 1992, Vol. 5, No.3, pp. 439-446, a copolymer having isobornylmethacrylate units, in R. D.Allen et al., Journal of Photopolymer Science and Technology, 1995, Vol.8, No. 4, pp. 623-636, and a resin including norbornene-maleic anhydridealternating copolymers, in F. M. Houlihan et al., Macromolecules 1997,Vol. 30, pp. 6517-6524.

[0013] However, monomers including alicyclic groups herein such as thosementioned above do not have polar groups (for instance, carboxyl groupsor hydroxy groups) having adhesion to a substrate. Hence, monopolymer ofmonomers having alicyclic groups has intensive hydrophobic nature, andpoor adhesion to a substrate (for instance, a silicon substrate),resulting in that a uniformly coated film cannot be well reproduced.

[0014] In addition, residues containing adamantine, isobonyl or menthyltherein, having resistance to dry etching, do not have residues whichcan exhibit a difference in solubility between before and after exposureto light. Hence, if monopolymer of these monomers are used, it would bedifficult to form a pattern by exposing them to light.

[0015] This problem can be solved by copolymerizing those monomers withcomonomers which can exhibit the solubility difference, such ast-butylmethacrylate or tetrahydromethacrylate, or with comonomers whichhave adhesion to a substrate, such as methacrylic acid.

[0016] Though the resultant copolymer has to contain comonomers thereinat about 50 mol %, the copolymer could have insufficient resistance todry etching, because of low resistance of a comonomer unit to dryetching.

[0017] The resist including norbornene—maleic anhydride alternatingcopolymers could have poor adhesion to a substrate, because of no polargroups in norbornene rings. In order to enhance adhesion to a substrate,it would be necessary, for instance, to copolymerize the resist withcomonomers having adhesion to a substrate, such as acrylic acid.

[0018] However, the resultant copolymer might have insufficientresistance to dry etching.

[0019] Polymers including a lactone structure have been suggested as aphotoresist material for use of ArF excimer laser beams (193 nm), whichprovides excellent resistance to etching and adhesion to a substrate, inJapanese Patent Application Publications Nos. 2000-159758, 2001-242627,and 2002-53571. Furthermore, Japanese Patent Application Publication No.2001-296661 has suggested a polymer including a lactone structure as amaterial of which a photoresist is composed for use of ArF excimer laserbeams (193 nm) and which has improved light-exposure margins.

[0020] However, there are not found any reports indicating that4-oxo-5-oxatetracyclo [7.2.1.0^(2,8).0^(3,7)] dodecyl skeleton (n=1 andX represents —CH₂—), 3-oxo-4-oxatricyclo [5.2.1.0^(2,6)] nonyl skeleton(n=0 and X represents —CH₂—) both defined in accordance with thelater-mentioned general formula (III), 4-oxo-5-oxatetracyclo[7.2.1.0^(2,8).0^(3,7)] dodecane-10,11-diyl skeleton defined inaccordance with the later-mentioned general formula (IV), and3-oxo-4-oxatricyclo [5.3.0.0^(2,6)] decane-8,10-dimethylene skeletondefined in accordance with the later-mentioned general formula (V), aswell as the above-mentioned conventional materials, are useful for achemically-amplified resist.

[0021] Though many suggestions have been made with respect to achemically-amplified resist, as mentioned above, further improvement isrequired.

[0022] In view of the above-mentioned problems, it is an object of thepresent invention to provide a chemically-amplified resist compositionhaving high transparency to light having a wavelength of 220 nanometersor smaller, resistance to etching, and adhesion to a substrate.

[0023] It is further an object of the present invention to provide apolymer (a resin of which a resist is composed) to be used for thechemically-amplified resist composition, unsaturated monomer thereof,and a method of forming a pattern through the use of thechemically-amplified resist composition.

DISCLOSURE OF THE INVENTION

[0024] In order to accomplish the above-mentioned objects, there isprovided a (metha)acrylate derivative having a bridged alicyclicγ-lactone structure defined in the general formula (I):

[0025] In the general formula (I), R¹ represents one of a hydrogen atomand a methyl group, R² and R³ each represents one of a hydrogen atom andan alkyl group having a carbon number in the range of 1 to 6 bothinclusive, or R² and R³ link each other, and each represents an alkylenegroup having a carbon number in the range of 1 to 6 both inclusive andcooperating with a carbon atom to which R² and R³ link to define a ring,X represents one of —CH₂— and —O—, Z represents one of a hydrogen atomand a methyl group, and n represents one of 0 and 1 wherein when nrepresents 0 and X represents —CH₂—, R² and R³ each represents a carbonnumber in the range of 1 to 6 both inclusive.

[0026] There is further provided an unsaturated monomer having a bridgedalicyclic γ-lactone structure defined in the general formula (II):

[0027] In the general formula (II), R⁴ and R⁵ each represents one of ahydrogen atom and an alkyl group having a carbon number in the range of1 to 6 both inclusive, or R⁴ and R⁵ link each other, and each representsan alkylene group having a carbon number in the range of 1 to 6 bothinclusive and cooperating with a carbon atom to which R⁴ and R⁵ link todefine a ring.

[0028] There is still further provided a polymer resulted frompolymerizing or copolymerizing a monomer composition containing at leastone of the above-mentioned (metha)acrylate derivative and theabove-mentioned unsaturated monomer.

[0029] There is yet further provided a polymer including at least one ofa repeated structural unit having a bridged alicyclic γ-lactonestructure defined in the general formula (III), a repeated structuralunit having a bridged alicyclic γ-lactone structure defined in thegeneral formula (IV), and a repeated structural unit having a bridgedalicyclic γ-lactone structure defined in the general formula (V).

[0030] In the general formula (III), R¹ represents one of a hydrogenatom and a methyl group, R² and R³ each represents one of a hydrogenatom and an alkyl group having a carbon number in the range of 1 to 6both inclusive, or R² and R³ link each other, and each represents analkylene group having a carbon number in the range of 1 to 6 bothinclusive and cooperating with a carbon atom to which R² and R³ link todefine a ring, X represents one of —CH₂— and —O—, Z represents one of ahydrogen atom and a methyl group, and n represents one of 0 and 1wherein when n represents 0 and X represents —CH₂—, R² and R³ eachrepresents a carbon number in the range of 1 to 6 both inclusive.

[0031] In the general formula (IV), R⁴ and R⁵ each represents one of ahydrogen atom and an alkyl group having a carbon number in the range of1 to 6 both inclusive, or R⁴ and R⁵ link each other, and each representsan alkylene group having a carbon number in the range of 1 to 6 bothinclusive and cooperating with a carbon atom to which R⁴ and R⁵ link todefine a ring.

[0032] In the general formula (V), R⁴ and R⁵ each represents one of ahydrogen atom and an alkyl group having a carbon number in the range of1 to 6 both inclusive, or R⁴ and R⁵ link each other, and each representsan alkylene group having a carbon number in the range of 1 to 6 bothinclusive and cooperating with a carbon atom to which R⁴ and R⁵ link todefine a ring.

[0033] In the above-mentioned polymer, the repeated structural unitdefined in accordance with the general formula (III), the repeatedstructural unit defined in accordance with the general formula (IV), andthe repeated structural unit defined in accordance with the generalformula (V) are not always necessary to be identical with one another.The polymer may contain two or more repeated structural units selectedfrom them. In the polymer, each of the structural units may have anysequence. Accordingly, the polymer may be a random copolymer, analternating copolymer or a block copolymer.

[0034] It is preferable that a content ratio of the repeated structuralunit defined in the general formula (III), (IV) or (V) to the polymer inits entirety is in the range of 5 to 100 mol % both inclusive.

[0035] It is preferable that a weight-average molecular weight of thepolymer is in the range of 2,000 to 200,000 both inclusive.

[0036] The present invention further provides a chemically-amplifiedresist composition containing one of the above-mentioned polymers.

[0037] It is preferable that the chemically-amplified resist compositioncontains one of the above-mentioned polymers, and a photo acid generatorwhich generates acid when exposed to light.

[0038] It is preferable in the chemically-amplified resist compositionthat a content of the photo acid generator is in the range of 0.2 to 30mass % both inclusive relative to a total content of the polymer and thephoto acid generator.

[0039] It is preferable that the photo acid generator generates acidwhen light having a wavelength in the range of 180 to 220 nanometersboth inclusive is irradiated thereto.

[0040] The present invention further provides a method of forming apattern, including at least the steps, in sequence, of coating theabove-mentioned chemically-amplified resist composition onto asubstrate, baking the chemically-amplified resist composition, exposingthe chemically-amplified resist composition to light having a wavelengthin the range of 180 to 220 nanometers both inclusive, baking thechemically-amplified resist composition, and developing thechemically-amplified resist composition.

[0041] As light to which the chemically-amplified resist composition isexposed, there may select ArF excimer laser beams, for instance.

[0042] Herein, the term “(co)polymerization” means monopolymerization orcopolymerization, as usually used.

[0043] The polymer in accordance with the present invention includes,among bridged alicyclic lactone skeletons, 4-oxo-5-oxatetracyclo[7.2.1.0^(2,8).0^(3,7)] dodecyl skeleton (n=1), 3-oxo-4-oxatricyclo[5.2.1.0^(2,6)] nonyl skeleton (n=0) both defined in accordance with thegeneral formula (III), 4-oxo-5-oxatetracyclo [7.2.1.0^(2,8).0^(3,7)]dodecane-10,11-diyl skeleton defined in accordance with the generalformula (IV), and 3-oxo-4-oxatricyclo [5.3.0.0^(2,6)]decane-8,10-dimethylene skeleton defined in accordance with the generalformula (V).

[0044] Hence, the chemically-amplified resist composition including thepolymer in accordance with the present invention has high transparencyto light having a wavelength of 220 nanometers or smaller, highresistance to etching and excellent adhesion to a substrate. The reasonstherefore are considered as follows.

[0045] First, the repeated structural structures defined in accordancewith the above-mentioned general formula (III), (IV) and (V) do notinclude aromatic rings. Hence, the chemically-amplified resistcomposition can have high transparency to light having a wavelength of220 nanometers or smaller. In general, a polymer not including aromaticrings can have high transparency to light having a wavelength of 220nanometers or smaller.

[0046] Second, the repeated structural structures defined in accordancewith the above-mentioned general formula (III), (IV) and (V) include abridged alicyclic structure having a high carbon-density, that is,tetracyclo [7.2.1.0^(2,8).0^(3,7)] dodecane skeleton, tricyclo[5.2.1.0^(2,6)] nonane skeleton or tricyclo [5.3.0.0^(2,6)] decaneskeleton. Hence, the chemically-amplified resist composition can haveresistance to dry etching.

[0047] Third, the repeated structural structures defined in accordancewith the above-mentioned general formula (III), (IV) and (V) include aγlactone structure. Hence, the chemically-amplified resist compositioncan have higher polarity than conventional ones, and accordingly, havemore excellent adhesion to a substrate.

[0048] A lactone structure generally has a higher dielectric constantthan the same of an ester structure, an ether structure and an alcoholstructure.

[0049] For instance, according to Chemistry Handbook edited by JapanChemistry Academy, Basic II, 3rd edition, 1984, pp. 502-504, comparisonbeing made among compositions having a carbon number of 4, aγ-butyrolactone has a dielectric constant of 39, an ethyl acetate has adielectric constant of 6.02, a diethyl ether has a dielectric constantof 4.335, and a 1-butanol has a dielectric constant of 17.51. Amonglactone structures, a γ-lactone structure has an optimal dielectricconstant, and hence, it can accomplish particularly excellent adhesionto a substrate.

[0050] As mentioned above, the repeated structural structures defined inaccordance with the above-mentioned general formula (III), (IV) and (V)include both a bridged alicyclic structure and a γ-lactone structure,they can accomplish desired transparency to light having a wavelength of220 nanometers or smaller, resistance to etching, and adhesion to asubstrate, by virtue of the multiplier effect of a molecular structureand a dielectric constant.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0051] (1) Unsaturated Monomer of which the Polymer in Accordance withthe Present Invention is Composed

[0052] The polymer in accordance with the present invention is obtainedby (co)polymerizing both or one of a (metha)acrylate derivative having abridged alicyclic γ-lactone structure defined in accordance with thegeneral formula (I) and a monomer composition including an unsaturatedmonomer having a bridged alicyclic γ-lactone structure defined inaccordance with the general formula (II).

[0053] In the general formula (I), R¹ represents one of a hydrogen atomand a methyl group, R² and R³ each represents one of a hydrogen atom andan alkyl group having a carbon number in the range of 1 to 6 bothinclusive, or R² and R³ link each other, and each represents an alkylenegroup having a carbon number in the range of 1 to 6 both inclusive andcooperating with a carbon atom to which R² and R³ link to define a ring,X represents one of —CH₂— and —O—, Z represents one of a hydrogen atomand a methyl group, and n represents one of 0 and 1 wherein when nrepresents 0 and X represents —CH₂—, R² and R³ each represents a carbonnumber in the range of 1 to 6 both inclusive.

[0054] In the general formula, R⁴ and R⁵ each represents one of ahydrogen atom and an alkyl group having a carbon number in the range of1 to 6 both inclusive, or R⁴ and R⁵ link each other, and each representsan alkylene group having a carbon number in the range of 1 to 6 bothinclusive and cooperating with a carbon atom to which R⁴ and R⁵ link todefine a ring.

[0055] The alkyl group having a carbon number in the range of 1 to 6both inclusive may be straight-chain type one or branch-type one. It ispreferable that the alkyl group has a carbon number of 1 or 2.

[0056] Specifically, as an alkyl group having a carbon number in therange of 1 to 6 both inclusive, there may be selected from a methylgroup, an ethyl group, a n-propyl group, an isopropyl group, a n-butylgroup, an isobutyl group, a n-pentyl group, or a n-hexyl group.

[0057] The alkylene group having a carbon number in the range of 1 to 6both inclusive may be branch-type one, but preferably straight-chaintype one. The alkylene group mentioned herein includes a polymethylenegroup. It is preferable that the alkylene group has a carbon number of 4or 5.

[0058] As an alkylene group having a carbon number in the range of 1 to6 both inclusive, there may be selected from a propylene group (atrimethylene group) [—(CH₂)₃—], a butylene group (a tetramethylenegroup) [—(CH₂)₄—], or a penthylene group (a pentamethylene group)[—(CH₂)₅—].

[0059] As the unsaturated monomer defined in accordance with the generalformula (I), there may be selected from the followings.

[0060] As the unsaturated monomer defined in accordance with the generalformula (II), there may be selected from the following monomers.

[0061] In the general formula (I), when n is equal to one (1), it isparticularly preferable that each of R² and R³ represents a hydrogenatom, a methyl group, an ethyl group or an alkylene group having acarbon number of 4 or 5, and when n is equal to zero (0), it isparticularly preferable that each of R² and R³ represents a methylgroup, an ethyl group or an alkylene group having a carbon number of 4or 5.

[0062] In the general formula (II), it is particularly preferable thateach of R⁴ and R⁵ represents a methyl group, an ethyl group or analkylene group having a carbon number of 4 or 5.

[0063] (2) Method of Manufacturing the Monomer in Accordance with thePresent Invention

[0064] The monomer defined in accordance with the above-mentionedgeneral formula (II) can be manufactured, for instance, by causingtricycle [4.2.1.02,5]-7-nonene-3,4-dicarboxylic acid anhydride to reactwith Grignard reagent, and treating the resultant with acid.

[0065] The monomer defined in accordance with the above-mentionedgeneral formula (I) can be manufactured, for instance, by causing eitherthe composition defined in accordance with the general formula (II) ortricycle 5-norbornene-2,3-dicarboxylic acid anhydride to react withGrignard reagent, treating the resultant with acid to generate lactonecompound, and either causing the lactone compound to react with(metha)acrylic acid under existence of acid catalyst, or turning thelactone compound into hydroxy compound in hydroborasion reaction, andcausing the resultant to react with (metha)acryloilchloride underexistence of basic catalyst.

[0066] (3) Polymer in Accordance with the Present Invention

[0067] The polymer in accordance with the present invention is obtainedby (co)polymerizing both or one of an unsaturated monomer having abridged alicyclic γ-lactone structure defined in accordance with thegeneral formula (I) and a monomer composition including an unsaturatedmonomer having a bridged alicyclic γ-lactone structure defined inaccordance with the general formula (II), and includes at least one of arepeated structural unit having the bridge alicyclic γ-lactone structuredefined in accordance with the general formula (III), a repeatedstructural unit having the bridge alicyclic γ-lactone structure definedin accordance with the general formula (IV), and a repeated structuralunit having the bridge alicyclic γ-lactone structure defined inaccordance with the general formula (V).

[0068] The repeated structural unit defined in accordance with thegeneral formula (III) is derived from the monomer defined in accordancewith the general formula (I). Each of the repeated structural unitsdefined in accordance with the general formulas (IV) and (V) is derivedfrom the monomer defined in accordance with the general formula (II).

[0069] The polymer in accordance with the present invention, having sucha structure as mentioned above is suitable for a resin of which a resistis composed.

[0070] In the general formula (III), R¹ represents one of a hydrogenatom and a methyl group, R² and R³ each represents one of a hydrogenatom and an alkyl group having a carbon number in the range of 1 to 6both inclusive, or R² and R³ link each other, and each represents analkylene group having a carbon number in the range of 1 to 6 bothinclusive and cooperating with a carbon atom to which R² and R³ link todefine a ring, X represents one of —CH₂— and —O—, Z represents one of ahydrogen atom and a methyl group, and n represents one of 0 and 1wherein when n represents 0 and X represents —CH₂—, R² and R³ eachrepresents a carbon number in the range of 1 to 6 both inclusive,

[0071] In the general formula (IV), R⁴ and R⁵ each represents one of ahydrogen atom and an alkyl group having a carbon number in the range of1 to 6 both inclusive, or R⁴ and R⁵ link each other, and each representsan alkylene group having a carbon number in the range of 1 to 6 bothinclusive and cooperating with a carbon atom to which R⁴ and R⁵ link todefine a ring.

[0072] In the general formula (V), R⁴ and R⁵ each represents one of ahydrogen atom and an alkyl group having a carbon number in the range of1 to 6 both inclusive, or R⁴ and R⁵ link each other, and each representsan alkylene group having a carbon number in the range of 1 to 6 bothinclusive and cooperating with a carbon atom to which R⁴ and R⁵ link todefine a ring.

[0073] The alkyl group having a carbon number in the range of 1 to 6both inclusive may be straight-chain type one or branch-type one. It ispreferable that the alkyl group has a carbon number of 1 or 2.

[0074] Specifically, as an alkyl group having a carbon number in therange of 1 to 6 both inclusive, there may be selected from a methylgroup, an ethyl group, a n-propyl group, an isopropyl group, a n-butylgroup, an isobutyl group, a n-pentyl group, or a n-hexyl group.

[0075] The alkylene group having a carbon number in the range of 1 to 6both inclusive may be branch-type one, but preferably straight-chaintype one. The alkylene group mentioned herein includes a polymethylenegroup. It is preferable that the alkylene group has a carbon number of 4or 5.

[0076] As an alkylene group having a carbon number in the range of 1 to6 both inclusive, there may be selected from a propylene group (atrimethylene group) [—(CH₂)₃—], a butylene group (a tetramethylenegroup) [—(CH₂)₄—], or a penthylene group (a pentamethylene group)[—(CH₂)₅—].

[0077] As the repeated structural unit defined in accordance with thegeneral formula (III), there may be selected from the followings.

[0078] As the repeated structural unit defined in accordance with thegeneral formula (IV), there may be selected from the followings.

[0079] As the repeated structural unit defined in accordance with thegeneral formula (V), there may be selected from the followings.

[0080] In the general formula (III), when n is equal to one (1), it isparticularly preferable that each of R² and R³ represents a hydrogenatom, a methyl group, an ethyl group or an alkylene group having acarbon number of 4 or 5, and when n is equal to zero (0), it isparticularly preferable that each of R² and R³ represents a methylgroup, an ethyl group or an alkylene group having a carbon number of 4or 5.

[0081] In the general formulas (IV) and (V), it is particularlypreferable that each of R⁴ and R⁵ represents a methyl group, an ethylgroup or an alkylene group having a carbon number of 4 or 5.

[0082] One or more unsaturated monomers defined in accordance with thegeneral formula (I) may be polymerized with one or more unsaturatedmonomers defined in accordance with the general formula (II).

[0083] The unsaturated monomers defined in accordance with the generalformula (I) are not always necessary to be identical with one another.Two or more monomers may be used, if they are defined in accordance withthe general formula (I).

[0084] The unsaturated monomers defined in accordance with the generalformula (II) are not always necessary to be identical with one another.Two or more monomers may be used, if they are defined in accordance withthe general formula (II).

[0085] In the polymer in accordance with the present invention, therepeated structural unit defined in accordance with the general formula(III), the repeated structural unit defined in accordance with thegeneral formula (IV), and the repeated structural unit defined inaccordance with the general formula (V) are not always necessary to beidentical with one another. The polymer may contain two or more repeatedstructural units, if they are defined in accordance with theabove-mentioned general formulas.

[0086] In the polymer in accordance with the present invention, each ofthe repeated structural units may have any sequence. Accordingly, thepolymer may be a random copolymer, an alternating copolymer or a blockcopolymer.

[0087] If necessary, it would be possible to accomplish broadercharacteristics by copolymerizing two or more monomers, and using apolymer including two or more repeated structural units.

[0088] The monopolymer of the unsaturated monomer defined in accordancewith the general formula (I) or the monopolymer of the unsaturatedmonomers defined in accordance with the general formula (II), or thecopolymer of at least one of two or more unsaturated monomers defined inaccordance with the general formula (I) and two or more unsaturatedmonomers defined in accordance with the general formula (II) has hightransparency to light having a wavelength of 220 nanometers or smaller,resistance to etching, and adhesion to a substrate.

[0089] By copolymerizing the polymer with other comonomers, the polymerin accordance with the present invention can have a structural unitincluding groups which can decompose acid derived from a photo acidgenerator, and a structural unit for accomplishing broadercharacteristics in a resin of which a chemically-amplified resist iscomposed, as well as the repeated structural units defined in accordancewith the general formulas (III), (IV) and (V).

[0090] In the above-mentioned case, each of the structural units mayhave any sequence. Accordingly, the polymer may be a random copolymer,an alternating copolymer or a block copolymer.

[0091] As a repeated structural unit derived from a comonomer to becopolymerized together, any one or more of the structural units definedin accordance with the general formulas (VI-a) to (VI-d) may bepreferably selected in view that broad characteristics can beaccomplished and associated monomers have sufficient polymerizability.

[0092] In the general formula (VI-a), R¹¹ represents a hydrogen atom ora methyl group, and R¹² represents a hydrogen atom, a group decomposableby acid, a bridged alicyclic hydrocarbon radical including a groupdecomposable by acid and having a carbon number in the range of 7 to 13both inclusive, a hydrocarbon radical having a carbon number in therange of 7 to 12 both inclusive, a bridged alicyclic hydrocarbon radicalincluding a hydroxy group or a carboxy group, and having a carbon numberin the range of 7 to 13 both inclusive, or a2,6-norbornanecarbolactone-5-yl group.

[0093] In the general formula (VI-b), R¹³ represents a hydrogen atom ora methyl group, and R¹⁴ represents a hydrogen atom, a hydroxy group, ahydroxyalkyl group, a carboxy group, or an acid-decomposable organicgroup decomposable by acid to generate a carboxy group, and having acarbon number of 20 or smaller. Each of X¹¹ and X¹² represents ahydrogen atom or a methyl group, and ml represents 0 or 1.

[0094] In the general formula (VI-c), R¹⁵ represents a hydrogen atom ora methyl group, and R¹⁶ represents a hydrogen atom, a hydroxy group, ahydroxyalkyl group, a carboxy group, or an acid-decomposable organicgroup decomposable by acid to generate a carboxy group, and having acarbon number of 20 or smaller. Each of X¹³ and X¹⁴ represents ahydrogen atom or a methyl group, and m² represents 0 or 1.

[0095] As a group decomposable by acid, there may be selected from at-butyl group, a tetrahydropyran-2-yl group, a tetrahydrofuran-2-ylgroup, a 4-metoxytetrahydropyran-4-yl group, a 1-ethoxyethyl group, a1-butoxyethyl group, a 1-propoxyethyl group, a 3-oxocyclohexyl group, a2-methyl-2-adamanthyl group, a 2-ethyl-2-adamanthyl group, a1-methyl-1-adamanthyl group, a 8-methyl-8-tricyclo [5.2.1.0^(2,6)] decylgroup, a 1,2,7,7-tetramethyl-2-norbornyl group, a 2-acetoxymenthylgroup, a 2-hydroxymenthyl group, and a 1-methyl-1-cyclohexylethyl group.

[0096] As a bridged alicyclic hydrocarbon radical including a groupdecomposable by acid and having a carbon number in the range of 7 to 13both inclusive, there may be selected from at-butoxycarbonyloxytetracyclododecyl group or at-butoxycarbonyloxynorbornyl group, as suggested in Japanese Patent No.2856116.

[0097] As a hydrocarbon radical having a carbon number in the range of 1to 12 both inclusive, there may be selected from a methyl group, anethyl group, a n-propyl group, an isoproplyl group, a n-butyl group, anisobutyl group, a t-butyl group, a cyclohexyl group, a tricycle[5.2.1.0^(2,6)] decyl group, an adamanthyl group, a norbonyl group, anisobonyl group, and a tetracyclo [4.4.0.1^(2,5.)1^(7,10)] dodecyl group.

[0098] As a bridged alicyclic hydrocarbon radical including a hydroxygroup or a carboxy group, and having a carbon number in the range of 7to 13 both inclusive, there may be selected from a hydroxyadamanthylgroup, a dihydroxyadamanthyl group, a hydroxynorbornyl group, ahydroxytetracyclododecyl group, a carboxyadamanthyl group, acarboxynorbornyl group, and a carboxytetracyclododecyl group.

[0099] As a hydroxyalkyl group, a hydroxymethyl group or a hydroxyethylgroup may be used.

[0100] As an acid-decomposable organic group decomposable by acid togenerate a carboxy group, and having a carbon number of 20 or smaller,there may be selected from a t-butoxycarbonyl group, atetrahydropyranyloxycarbonyl group, a4-methoxytetrahydropyranyloxycarbonyl group, a 1-ethoxyethoxycarbonylgroup, a tetrahydrofuranyloxycarbonyl group, a 1-butoxyethoxycarbonylgroup, a 1-propoxyethoxycarbonyl group, a 3-oxocyclohexyloxycarbonylgroup, a 2-methyl-2-adamanthyloxycarbonyl group, a2-ethyl-2-adamanthyloxycarbonyl group, a 8-methyl-8-tricyclo[5.2.1.0^(2,6)] decyloxycarbonyl group,1,2,7,7-tetramethyl-2-norbornyloxycarbonyl group, a2-acetoxymenthyloxycarbonyl group, a 2-hydroxymenthyloxycarbonyl group,and a 1-methyl-1-cyclohexylethoxycarbonyl group.

[0101] It is preferable that a content ratio of the structural unitdefined in the general formula (III), (IV) or (V) in the polymer in itsentirety is in the range of 5 to 100 mol % both inclusive.

[0102] When the polymer is copolymerized with other comonomers, acontent ratio of the structural unit defined in the general formula(III), (IV) or (V) in the resultant copolymer in its entirety is in therange of preferably 5 mol % or greater, more preferably 7 mol % orgreater, and most preferably 10 mol % or greater.

[0103] A content ratio of the structural unit defined in the generalformula (III), (IV) or (V) in the copolymer in its entirety is in therange of preferably 90 mol % or smaller, more preferably 80 mol % orsmaller, and most preferably 70 mol % or smaller.

[0104] A weight-average molecular weight of the polymer in accordancewith the present invention is in the range of 2,000 to 200,000 bothinclusive regardless of whether the polymer is a monopolymer or acopolymer.

[0105] (4) Method of Manufacturing the Polymer in Accordance with thePresent Invention

[0106] The polymer having the above-mentioned structure, in accordancewith the present invention, can be manufactures by a conventionalpolymerization process such as radical polymerization, anionpolymerization, addition polymerization or ring opening metathesispolymerization.

[0107] In radical polymerization, the polymer can be manufactured by,for instance, adding suitable initiator (for instance,azobisisobutyronitrile (AIBN)) of radical polymerization to drytetrahydrofuran in inert gas (for instance, argon or nitrogen)atmosphere, and heating and stirring the resultant at a temperature inthe range of 50 to 70 degrees centigrade for 0.5 to 12 hours.

[0108] A volume of the initiator of radical polymerization may bedetermined to any volume. An organic solvent to be used is not to belimited to tetrahydrofuran, but any organic solvent may be used.

[0109] In addition polymerization, the polymer can be manufacturedthrough the use of palladium compound such as (η³-allyl) Pd (BF₄),(η³-allyl) Pd (SbF₆), [Pd(CH₃CN)₄] [BF₄]₂ as a catalyst in accordancewith the method suggested by J. P. Mathew in Macromolecules, 1966, Vol.29, pp. 2755-2763.

[0110] As an alternative, the polymer can be manufactured through theuse of nickel compound such as bis(pentafluorophenyl) nickel toluenecomplex in accordance with the method suggested by T. Chiba et al. inJournal of Photopolymer Science and Technology, 2000, Vol. 13, No. 4,pp. 657-664.

[0111] In ring opening metathesis polymerization, the polymer can bemanufactured by carrying out ring-opening polymerization through the useof a metathesis catalyst, and hydrogenating the resultant through theuse of a noble-metal catalyst such as palladium.

[0112] As a metathesis catalyst, there may be selected from halides oftransition metals such as tungsten (W), molybdenum (Mo), or rhenium(Re), specifically, from WCl₆, MoCl₅ and ReCl₃. A metathesis catalyst isnot to be limited to those compounds. As a metathesis catalyst, theremay be also used halides of the above-mentioned transition metals, andorganic metal compounds such as organic aluminum compounds.

[0113] (5) The Chemically-Amplified Resist Compound in Accordance withthe Present Invention

[0114] The chemically-amplified resist compound in accordance with thepresent invention is composed of mixture of the above-mentioned polymerin accordance with the present invention and a photo acid generatorwhich generates acid when exposed to light.

[0115] The chemically-amplified resist compound in accordance with thepresent invention generally further includes a solvent for solving thepolymer and the photo acid generator. The polymer in accordance with thepresent invention may contain one or more solvents.

[0116] A photo acid generator to be used for the invention preferablygenerates an acid when exposed to light preferably having a wavelengthequal to or smaller than 400 nm, and more preferably, in the range of180 to 220 nm both inclusive.

[0117] In the present invention, any photo acid generator may be used ifa mixture of the polymer and the photo acid generator is sufficientlysoluble in a solvent, and further if it is possible to form a uniformcoating film by means of a film-forming process such as a spin-coatingprocess. One or more photo acid generators may be mixed in theinvention.

[0118] Photo acid generators usable for reducing the present inventioninto practice may be selected, for instance, from any one oftriphenylsulfonium salt derivatives, sulfonium salt derivativessuggested in Japanese Patent Application Publication No. 2001-294570,alkylsulfonium salt derivatives having a bridged cyclic alkyl group,suggested in Japanese Patent No. 2964990, dialkyl-2-oxoalkylsulfoniumsalt derivatives suggested in Japanese Patent Application PublicationNo. 2001-354669, trialkylsulfonium salt derivatives. diphenyliodoniumsalt derivatives, dialkylphenasylsulfonium salt derivatives,nitrobenzylsulfonate derivatives, sulfonate derivatives ofN-hydroxysuccinimide.

[0119] A content of a photo acid generator is preferably 0.2 mass % orgreater, and more preferably, 1 mass % or greater relative to a totalmass of the polymer and the photo acid generator so as to accomplishsufficient sensitivity of the chemically-amplified resist compositionand form a desired pattern.

[0120] Furthermore, the content of a photo acid generator is preferably30 mass % or smaller, and more preferably 15 mass % or smaller so as touniformly form a film and suppress generation of residue (scum) afterdevelopment.

[0121] If necessary, a suitable solvent is used for preparing thechemically-amplified resist composition in accordance with the presentinvention.

[0122] In the present invention, any solvent may be used if it can wellsolve the polymer and the photo acid generator, and further if solutionof the solvent can be uniformly coated onto an object by a film-coatingprocess such as a spin-coating process. A single solvent or a mixture oftwo or more solvents may be used.

[0123] Specifically, a solvent to be used in the invention is selectedfrom any one of n-propyl alcohol, isopropyl alcohol, n-butyl alcohol,tert-butyl alcohol, propyleneglycolmonomethylether acetate,propyleneglycolmonoethylether acetate, methyl lactate, ethyl lactate,2-methoxybutyl acetate, 2-ethoxyethyl acetate, pyrubic acid methyl,pyrubic acid ethyl, 3-methoxypropionatemethyl, 3-methoxypropionateethyl,N-methyl-2-pyrrolidinone, cyclopentanone, cyclohexanol,methylethylketone, 1,4-dioxan, ethyleneglycolmonomethylether, ethyleneglycolmonomethylether acetate, ethylene glycolmonoethylether,ethyleneglycolmonoisopropylether, diethyleneglycolmonomethylether, anddiethyleneglycoldimethylether.

[0124] A content of a solvent in the chemically-amplified resistcomposition in accordance with the present invention, comprised of apolymer, a photo acid generator and a solvent, is determined inaccordance with a thickness of a resist to be formed.

[0125] If necessary, the chemically-amplified resist composition inaccordance with the present invention may include other components suchas an agent for avoiding dissolution, basics, a surface active agent,pigments, a stabilizer, an agent for improving coating characteristic,and dyes.

[0126] (6) Method of Forming a Pattern, in Accordance with the PresentInvention

[0127] Hereinbelow is explained an example of a method of forming apattern in accordance with the present invention. The method may use theabove-mentioned chemically-amplified resist composition in accordancewith the present invention.

[0128] First, the chemically-amplified resist composition in accordancewith the present invention is coated onto a substrate by a spin-coatingprocess or any other suitable process.

[0129] Then, the substrate on which the chemically-amplified resistcomposition has been coated is baked (pre-baked) to thereby dry thecoated film. Thus, there is formed a resist film on the substrate.

[0130] Then, the thus formed resist film is exposed through a photomaskto light having a wavelength in the range of 180 to 220 nanometers bothinclusive. As light to which the resist film is to be exposed ispreferably ArF excimer laser beams.

[0131] After exposure to the light, the resist film is baked, and then,developed. Any conventional developing solution may be used. Afterdevelopment, if necessary, the substrate is rinsed with pure water.Thus, a resist pattern is formed on the substrate.

[0132] Then, the substrate on which the resist pattern has been formedis baked (post-baked).

EXAMPLES

[0133] Hereinbelow, the present invention is explained in detail inconnection with examples. However, it should be noted that the presentinvention is not to be limited to those examples.

[0134] Unless otherwise indicated, reagents used are available oneshaving high purity.

Example 1

[0135] There was synthesized 4-oxo-5-oxatetracyclo[7.2.1.0^(2,8.)0^(3,7)]-10-dodecene having the structure indicatedbelow, that is, a monomer defined in accordance with the general formula(II) wherein R⁴ and R⁵ each represents a hydrogen atom.

[0136] First, sodium boron hydride of 4.46 grams was dispersed in drytetrahydrofuran (hereinafter, referred to simply as “THF”) of 50 ml.Then, while cooled by ices, solution obtained by solving tricycle[4.2.1.0^(2,5)]-7-nonene-3,4-dicarboxylic acid anhydride (synthesized inaccordance with the method suggested in J. Am. Chem. Soc. Vol. 94, pp.787-792) of 20 grams into THF of 100 ml was dropped to the mixture ofsodium boron hydride and THF.

[0137] The resultant was stirred for two hours at room temperature, andthen, 0.5N hydrochloric acid was added to the resultant to make theresultant acidic. Then, under a reduced pressure, a solvent was removedat 50 degrees centigrade. Then, diethyl ether of 200 ml was added to theresidue, and then, washed with brine.

[0138] After the organic layer was dried with MgSO₄, diethyl ether wasremoved under a reduced pressure. Then, chloroform of 200 ml and furthersilica gel were added to the resultant to thereby remove impurities byabsorption. Then, a solvent was removed under a reduced pressure. Then,the residue was recombined with ligroin. Thus, there was obtained atarget material by 6 grams. The yield was 32%.

[0139] The measurement results of ¹H-NMR (reference sample: CDCl₃) ofthe obtained target material were as follows.

[0140] δ: 0.1.4 (1H, d), 1.59 (1H, d), 1.94-1.98 (1H, m), 2.12-2.16 (1H,m), 2.44-2.51 (1H, m), 2.6 (1H, dd), 2.83 (1H, s), 2.94 (1H, s), 4.36(1H, dd), 4.51 (1H, dd), 6.03 (1H, s).

Example 2

[0141] There was synthesized 4-oxo-5-oxa-6,6-dimethyltetracyclo[7.2.1.0^(2,8).0^(3,7)]-10-dodecene having the structure indicatedbelow, that is, a monomer defined in accordance with the general formula(II) wherein R⁴ and R⁵ each represents a methyl group.

[0142] First, solution obtained by solving tricycle[4.2.1.0^(2,5)]-7-nonene-3,4-dicarboxylic acid anhydride of 20 gramsinto dry THF of 200 ml while cooled with ices was dropped to diethylether solution (3 mol/liter) of methylmagnesiumbromide of 110 ml inargon atmosphere.

[0143] The resultant was stirred for two hours at room temperature, andthen, 10% hydrochloric acid was added to the resultant, while cooledwith ices, to make the resultant acidic. Then, the resultant was stirredfor an hour at 40 degrees centigrade. Then, diethyl ether of 200 ml wasadded to the resultant. Then, the organic layer was washed with 4%aqueous solution of sodium carbonate and further saturated brine inturn, and thereafter, was dried with magnesium sulfate.

[0144] Then, dimethyl ether was removed under a reduced pressure. Then,the residue was recombined with ligroin-toluene. Thus, there wasobtained a target material by 6.92 grams. The yield was 32%.

[0145] The measurement results of ¹H-NMR (reference sample: CDCl₃) ofthe obtained target material were as follows.

[0146] δ: 1.35 (3H, s), 1.37 (1H, d), 1.48 (3H, s), 1.57 (1H, d),1.97-2.01 (1H, m), 2.06-2.1 (1H, m), 2.13-2.18 (1H, m), 2.71-2.75 (2H,m), 2.93 (1H, s), 6.03 (2H, s).

Example 3

[0147] There was synthesized acrylate having the structure indicatedbelow, that is, acrylate defined in accordance with the general formula(I) wherein R¹ represents a hydrogen atom, R² and R³ each represents amethyl group, X represents —CH₂—, Z represents a hydrogen atom, and n isequal to one (1).

[0148] First, THF solution (1 mol/L) of BH₃ THF complex salt of 21 mlwas dropped, while cooled with ices, into a solution obtained by solvingthe monomer of 7.8 grams obtained in Example 2 into dry THF of 200 ml.

[0149] The resultant was stirred for an hour while cooled with ices andfurther for an hour at room temperature, and then, water of 3 ml, NaOHaqueous solution (3 mol/L) of 7 ml, and 30% hydrogen peroxide solutionof 4.6 ml were dropped in turn into the resultant.

[0150] Then, the resultant was stirred for two hours at roomtemperature. Then, diethyl ether of 100 ml was added to the resultant.Then, the diethyl ether organic layer was washed with saturated brine,and thereafter, was dried with magnesium sulfate. Then, a solvent wasremoved under a reduced pressure. Thus, there was quantitativelyobtained alcohol.

[0151] Then, alcohol of 4.88 grams, N,N-dimethylaniline of 3.99 grams,and phenothiazine of 10 mg were solved into dry methylene chloride of 40ml, and then, acryloil chloride of 2.38 grams were dropped into theresultant while cooled with ices. After the resultant was stirred forfour hours at room temperature, diethylether of 150 ml was added to theresultant. Then, the resultant was washed with 0.5N hydrochloric acid,3% aqueous solution of sodium carbonate and further brine, andthereafter, was dried with magnesium sulfate.

[0152] After a solvent was removed under a reduced pressure, the residuewas purified in a silica-gel column (solvent for elution: hexane/ethylacetate=2/1). Thus, there was obtained a target material, that is,acrylate by 2 grams in the form of transparent liquid. The yield was33%.

[0153] The measurement results of ¹H-NMR (reference sample: CDCl₃) ofthe obtained acrylate were as follows.

[0154] δ: 1.287, 1.292, 1.47, 1.49 (6H, s), 1.51-1.81 (4H, m), 2.1-2.49(5H, m), 2.78-2.84 (1H, m), 4.52-4.59 (1H, m), 5.82 (1H, dd), 6.09 (1H,dd), 6.38 (1H, d).

[0155] The measurement results of 1R (KBr disc) were as follows.

[0156] 1R (KBr disc): 2969 cm⁻¹ [ν(C—H)], 1766 cm⁻¹, 1722 cm⁻¹ [ν(C═O)],1635 cm⁻¹, 1619 cm⁻¹ [ν(C═C)], 1274 cm⁻¹, 1194 cm⁻¹.

Example 4

[0157] There was synthesized acrylate having the structure indicatedbelow, that is, acrylate defined in accordance with the general formula(I) wherein R¹ represents a hydrogen atom, R² and R³ each represents amethyl group, X represents —CH₂—, Z represents a hydrogen atom, and n isequal to zero (0).

[0158] First, solution obtained by solving 5-norbornene-2,3-dicarboxylicacid anhydride of 34.47 grams into dry THF of 100 ml was dropped, whilecooled with ices, into diethyl ether solution (3 mol/L) ofmethylmagnesiumbromide of 250 grams in argon atmosphere.

[0159] The resultant was stirred for two hours at room temperature, andthen, 10% hydrochloric acid was added to the resultant to make theresultant acidic. Then, the resultant was stirred for an hour at 40degrees centigrade. Then, diethyl ether of 200 ml was added to theresultant. Then, the resultant was washed with 3% aqueous solution ofsodium carbonate and further brine in turn, and thereafter, was driedwith magnesium sulfate.

[0160] After a solvent was removed, the residue was distillated under areduced pressure (106-107 degrees centigrade/0.6 mmHg). Thus, there wasobtained 3-oxo-4-oxa-5,5-dimethyltricyclo [5.2.1.0^(2,6)]-8-nonene of20.12 grams.

[0161] Then, 3-oxo-4-oxa-5,5-dimethyltricyclo [5.2.1.0^(2,6)]-8-noneneof 20 grams was solved into dry THF of 50 ml, into which THF solution (1mol/L) of BH₃ THF complex salt of 67 ml was dropped in argon atmospherewhile cooled with ices.

[0162] The resultant was stirred for an hour while cooled with ices andfurther for an hour at room temperature, and then, water of 10 ml, NaOHaqueous solution (3 mol/L) of 22 ml, and 30% hydrogen peroxide solutionof 15 ml were dropped in turn into the resultant.

[0163] Then, the resultant was stirred for two hours at roomtemperature. Then, diethyl ether of 200 ml was added to the resultant.Then, the diethyl ether organic layer was washed with saturated brine,and thereafter, was dried with magnesium sulfate. Then, a solvent wasremoved under a reduced pressure. Thus, there was quantitativelyobtained alcohol.

[0164] Then, alcohol of 20 grams, N,N-dimethylaniline of 18.4 grams, andphenothiazine of 50 mg were solved into dry methylene chloride of 200ml, and then, acryloil chloride of 10.96 grams were dropped into theresultant while cooled with ices.

[0165] After the resultant was stirred for four hours at roomtemperature, diethylether of 150 ml was added to the resultant. Then,the resultant was washed with 0.5N hydrochloric acid, 3% aqueoussolution of sodium carbonate and further brine in turn, and thereafter,was dried with magnesium sulfate.

[0166] After a solvent was removed under a reduced pressure, the residuewas purified in a silica-gel column (solvent for elution: hexane/ethylacetate=2/1). Thus, there was obtained a target material, that is,acrylate by 10.2 grams in the form of transparent liquid. The yield was40%.

[0167] The measurement results of ¹H-NMR (reference sample: CDCl₃) ofthe obtained acrylate were as follows.

[0168] δ: 1.36(3H, s), 1.38(3H, m), 1.40-1.65(2H, m), 2.4-2.9(6H, m),4.5-4.54(1H, m), 5.82(1H, dd), 6.09(1H, dd), 6.38(1H, d).

[0169] The measurement results of 1R (KBr disc) were as follows.

[0170] 1R (KBr disc): 2968 cm⁻¹ [ν(C—H)], 1768 cm⁻¹, 1720 cm⁻¹ [ν(C═O)],1636 cm⁻¹, 1618 cm⁻¹ [ν(C═C)],

Example 5

[0171] There was synthesized methacrylate having the structure indicatedbelow, that is, methacrylate defined in accordance with the generalformula (I) wherein R¹ represents a methyl group, R² and R³ eachrepresents a hydrogen atom, X represents —CH₂—, Z represents a hydrogenatom, and n is equal to one (1).

[0172] First, the monomer of 5 grams obtained in Example 1 andmethacrylic acid of 4.2 grams were solved into dry toluene of 20 ml, andphosphotungstic acid•n-hydrates of 0.279 grams were added thereto.

[0173] Then, the resultant was stirred for three hours at 80 degreescentigrade. Then, diethyl ether of 100 ml was added to the resultant.Then, the resultant was washed with 3% aqueous solution of sodiumcarbonate and further brine in turn, and thereafter, was dried withmagnesium sulfate.

[0174] After a solvent was removed, the residue was purified in asilica-gel column (solvent for elution: hexane/ethyl acetate=2/1). Thus,there was obtained a target material, that is, methacrylate by 1 gram.The yield was 13%.

[0175] The measurement results of 1R (KBr disc) for the obtainedmethacrylate were as follows.

[0176] 1R (KBr disc): 2969 cm⁻¹ [ν(C—H)], 1765 cm⁻¹, 1722 cm⁻¹ [ν(C═O)],1638 cm⁻¹ [ν(C═C)],

Example 6

[0177] There was synthesized acrylic polymer comprised of a structuralunit by 30 mol % which is defined in accordance with the general formula(III) wherein R¹ represents a hydrogen atom, R² and R³ each represents amethyl group, X represents —CH₂—, Z represents a hydrogen atom, and n isequal to one (1), a structural unit by 50 mol % which is defined inaccordance with the general formula (VI-a) wherein R¹¹ represents amethyl group, and R¹² represents a 2-methyl-2-adamantyl group, and astructural unit by 20 mol % which is defined in accordance with thegeneral formula (VI-a) wherein R¹¹ represents a methyl group, and R¹²represents a 3-hydroxy-1-adamantyl group.

[0178] In a 100 ml-flask with a reflux tube, acrylate of 2 gramsobtained in Example 3,2-methyl-2-adamantylmethacrylate of 2.82 grams,and 3-hydroxyadamantylmethacrylate of 1.14 grams were solved in drytetrahydrofuran of 40 ml. Further, AIBN of 158 mg (4 mol %) was addedthereto.

[0179] Then, the resultant was stirred for four hours at 65-67 degreescentigrade in argon atmosphere, and then, naturally cooled. Theresultant was poured into hexane of 400 ml, and the resultantprecipitate was filtered.

[0180] Then, the resultant was reprecipitated and then purified. As aresult, there was obtained a target material of 3.52 grams. The yieldwas 59%.

[0181] A copolymerization ratio of the obtained polymer was 30:50:20(mol ratio), based on an integration ratio of ¹H-NMR. Furthermore, aweight average molecular weight (Mw) and a degree of dispersion (Mw/Mn)of the obtained polymer were 9700 (equivalence in polystyrene) and 1.91,respectively, based on GPC analysis.

Example 7

[0182] There was synthesized a polymer in the same manner as Example 6except that a monomer ratio, namely, acrylate obtained in Example 3:2-methyl -2-adamantylmethacrylate: 3-hydroxyadamantylmethacrylate wasset to be 0.15:0.55:0.3 (mol ratio).

[0183] A copolymerization ratio of the obtained polymer was0.15:0.54:0.31 (mol ratio), based on an integration ratio of ¹H-NMR.Furthermore, a weight average molecular weight (Mw) of the obtainedpolymer was 8400.

Example 8

[0184] There was synthesized a polymer in the same manner as Example 6except that a monomer ratio, namely, acrylate obtained in Example 3:2-methyl -2-adamantylmethacrylate: 3-hydroxyadamantylmethacrylate wasset to be 0.45:0.45:0.1 (mol ratio).

[0185] A copolymerization ratio of the obtained polymer was0.44:0.46:0.1 (mol ratio), based on an integration ratio of ¹H-NMR.Furthermore, a weight average molecular weight (Mw) of the obtainedpolymer was 10500.

Example 9

[0186] There was synthesized a polymer in the same manner as Example 6except that a content (concentration) of AIBN was set equal to 0.5 mol%.

[0187] A copolymerization ratio of the obtained polymer was0.30:0.51:0.19 (mol ratio), based on an integration ratio of ¹H-NMR.Furthermore, a weight average molecular weight (Mw) of the obtainedpolymer was 43000.

Example 10

[0188] There was synthesized a polymer in the same manner as Example 6except that a content (concentration) of AIBN was set equal to 10 mol %.

[0189] A copolymerization ratio of the obtained polymer was0.29:0.51:0.2 (mol ratio), based on an integration ratio of ¹H-NMR.Furthermore, a weight average molecular weight (Mw) of the obtainedpolymer was 3900.

Example 11

[0190] There was synthesized acrylic polymer comprised of a structuralunit by 30 mol % which is defined in accordance with the general formula(III) wherein R¹ represents a hydrogen atom, R² and R³ each represents amethyl group, X represents —CH₂—, Z represents a hydrogen atom, and n isequal to one (1), a structural unit by 50 mol % which is defined inaccordance with the general formula (VI-a) wherein R¹¹ represents ahydrogen atom, and R¹² represents a t-butoxycarbonyltetracyclododecylgroup, and a structural unit by 20 mol % which is defined in accordancewith the general formula (VI-a) wherein R¹¹ represents a methyl group,and R¹² represents a carboxytetracyclododecyl group.

[0191] There was obtained the polymer by carrying out polymerization inthe same manner as Example 6 except thatt-butoxycarbonyltetracyclododecyl acrylate was employed in place of2-methyl-2-adamantylmethacrylate, andcarboxytetracyclododecylmethacrylate was employed in place of 3-hydroxy-1-adamantylmethacrylate. The yield was 54%.

[0192] A weight average molecular weight (Mw) and a degree of dispersion(Mw/Mn) of the obtained polymer were 10500 and 1.79, respectively, basedon GPC analysis.

Example 12

[0193] There was synthesized acrylic polymer comprised of a structuralunit by 30 mol % which is defined in accordance with the general formula(III) wherein R¹ represents a hydrogen atom, R² and R³ each represents amethyl group, X represents —CH₂—, Z represents a hydrogen atom, and n isequal to one (1), a structural unit by 50 mol % which is defined inaccordance with the general formula (VI-a) wherein R¹¹ represents amethyl group, and R¹² represents a 2-methyl-2-adamantyl group, and astructural unit by 20 mol % which is defined in accordance with thegeneral formula (VI-a) wherein R¹¹ represents a hydrogen atom, and R¹²represents a 2,6-norbornanecarbolactone-5-yl group.

[0194] There was obtained the polymer by carrying out polymerization inthe same manner as Example 6 except that5-acryloiloxy-2,6-norbornanecarbolactone was employed in place of3-hydroxy-1-adamantylmethacrylate. The yield was 51%.

[0195] A weight average molecular weight (Mw) and a degree of dispersion(Mw/Mn) of the obtained polymer were 9100 and 1.92, respectively, basedon GPC analysis.

Example 13

[0196] There was synthesized acrylic polymer comprised of a structuralunit by 30 mol % which is defined in accordance with the general formula(III) wherein R¹ represents a hydrogen atom, R² and R³ each represents amethyl group, X represents —CH₂—, Z represents a hydrogen atom, and n isequal to zero (0), a structural unit by 50 mol % which is defined inaccordance with the general formula (VI-a) wherein R¹¹ represents amethyl group, and R¹² represents a 2-methyl-2-adamantyl group, and astructural unit by 20 mol % which is defined in accordance with thegeneral formula (VI-a) wherein R¹¹ represents a methyl group, and R¹²represents a 3-hydroxy-1-adamantyl group.

[0197] There was obtained the polymer by carrying out polymerization inthe same manner as Example 6 except that acrylate obtained in Example 4was employed in place of acrylate obtained in Example 3. The yield was57%.

[0198] A weight average molecular weight (Mw) and a degree of dispersion(Mw/Mn) of the obtained polymer were 10400 and 1.88, respectively, basedon GPC analysis.

Example 14

[0199] There was synthesized polymer comprised of a structural unit by25 mol % which is defined in accordance with the general formula (IV)wherein R⁴ and R⁵ each represents a hydrogen atom, a structural unit by25 mol % which is defined in accordance with the general formula (VI-d),and a structural unit by 50 mol % which is defined in accordance withthe general formula (VI-a) wherein R¹¹ represents a methyl group, andR¹² represents a 2-methyl-2-adamantyl group.

[0200] There was obtained the polymer by carrying out polymerization inthe same manner as Example 6 except that monomer obtained in Example 1was employed in place of monomer obtained in Example 3, and that maleicanhydride was employed in place of 3-hydroxy-1-adamantylmethacrylate.The yield was 31%.

[0201] A weight average molecular weight (Mw) and a degree of dispersion(Mw/Mn) of the obtained polymer were 8400 and 2.55, respectively, basedon GPC analysis.

Example 15

[0202] There was synthesized polymer comprised of a structural unit by50 mol % which is defined in accordance with the general formula (IV)wherein R⁴ and R⁵ each represents a methyl group, and a structural unitby 50 mol % which is defined in accordance with the general formula(VI-b) wherein R¹³ represents a hydrogen atom, R¹⁴ represents at-butoxycarbonyl group, and X¹¹ and X¹² each represents a hydrogen atom,and m¹ is equal to zero (0).

[0203] First, di-μ-chlorobis[(η-aryl) palladium (II)] of 0.101 grams andhexafluoroantimony acid silver of 0.191 grams were solved in methylenechloride of 30 ml. The solution was stirred for twenty minutes at roomtemperature, and thereafter, the resultant mixture was filtered.

[0204] Then, the filtrate was added to a mixture of the monomer of 2.84grams obtained in Example 2,5-norbornene-2-carboxylic acid t-butyl esterof 2.694 grams, and methylene chloride of 10 ml.

[0205] Then, the resultant was stirred for 24 hours at room temperature,and thereafter, was added to methanol of 400 ml to separate precipitatedresin.

[0206] Then, the resultant resin was solved into methylene chloride of40 ml. Then, methanol of 4 ml and sodium boron hydride of 0.4 grams wereadded to the resultant solution.

[0207] The solution was stirred for three hours at room temperature, andwas left for 24 hours at room temperature. Thereafter, precipitatedparticles of Pd(0) were filtered out, and the filtrate was poured intomethanol of 400 ml to separate precipitated resin. Thus, there wasobtained a target material of 1.77 grams. The yield was 30%.

[0208] A weight average molecular weight (Mw) and a degree of dispersion(Mw/Mn) of the obtained polymer were 14000 and 2.44, respectively, basedon GPC analysis.

Example 16

[0209] There was synthesized acrylic polymer comprised of a structuralunit by 100 mol % which is defined in accordance with the generalformula (III) wherein R¹ represents a hydrogen atom, R² and R³ eachrepresents a methyl group, X represents —CH₂—, Z represents a hydrogenatom, and n is equal to one (1).

[0210] Acrylate of 0.6 grams obtained in Example 3 was solved in dry THFof 3 ml. Further, AIBN of 0.0143 g was added thereto.

[0211] Then, the resultant was stirred for four hours at 65-67 degreescentigrade in argon atmosphere, and then, naturally cooled. Theresultant mixture was poured into hexane of 50 ml, and the resultantprecipitate was filtered.

[0212] Then, the resultant was reprecipitated and then purified. As aresult, there was obtained a target material of 0.44 grams. The yieldwas 73%.

[0213] A weight average molecular weight (Mw) and a degree of dispersion(Mw/Mn) of the obtained polymer were 11200 and 2.12, respectively, basedon GPC analysis.

[0214] [Estimate of Resistance to Etching]

[0215] Acrylic polymer of 2 grams obtained in Example 6 was solved intopropyleneglycolmonomethyletheracetate of 10 grams, and was filtered witha Teflon filter of 0.2 micrometers.

[0216] Then, the filtrate was coated onto a 3-inch silicon substrate bya spin-coating process. Then, the substrate was baked on a hot plate for60 seconds at 90 degrees centigrade. Thus, there was formed a thin filmhaving a thickness of 0.7 micrometers.

[0217] The film was etched by means of a reactive ion etching (RIE)apparatus available from Nichiden Anelva as the model DEM 451. Then, anetching rate to CF₄ gas was measured

[0218] Etching conditions were as follows.

[0219] Power: 100 W

[0220] Pressure: 5 Pa

[0221] Gas flow rate: 30 sccm

[0222] Etching rates were measured in the same way with respect toacrylic polymer obtained in Example 11 and norbornane polymer obtainedin Example 15.

[0223] As reference samples, etching rates were measured in the same waywith respect to commercially available novolak resist,poly(p-vinylphenol) used as base resin for KrF resist, andpoly(methylmethacrylate) which is a resin having no bridged alicyclichydrocarbon radical in its molecular structure.

[0224] The measurement results are shown in Table 1. The etching ratesare standardized with respect to novolak resist. TABLE 1 Etching rate(Relative ratio) Example 6 1.02 Example 11 1.02 Example 15 0.98Poly(methylmethacrylate) 1.9 Poly(p-vinylphenol) 1.2 Novolak resist 1

[0225] It was proved that the polymer (Examples 6, 11 and 15) inaccordance with the present invention had a higher etching rate to CF₄gas and higher resistance to dry etching than the resins listed asreference samples.

[0226] [Estimate to Transparency]

[0227] Acrylic polymer of 1.8 grams obtained in Example 6 was solvedinto propyleneglycolmonomethyletheracetate of 10 grams, and was filteredwith a Teflon filter of 0.2 micrometers.

[0228] Then, the filtrate was coated onto a 3-inch quartz substrate by aspin-coating process. Then, the substrate was baked on a hot plate for60 seconds at 90 degrees centigrade. Thus, there was formed a thin filmhaving a thickness of 0.4 micrometers.

[0229] Then, transmittance of the thin film was measured by means of aspectrophotometer for ultraviolet and visible region, with respect to193.4 nm as a primary wavelength of ArF excimer laser beams.

[0230] Further, transmittances of acrylic polymer obtained in Example 11and norbornane polymer obtained in Example 15 were measured in the sameway.

[0231] The measurement results were shown in Table 2. TABLE 2Transmittance at a wavelength of 193.4 nm Example 6 81% Example 11 80%Example 15 69%

[0232] It was proved that the polymer (Examples 6, 11 and 15) inaccordance with the present invention had transparency sufficient tocompose a single-layer resist of the polymer.

[0233] [Estimate to Patterning]

[0234] A mixture of acrylic polymer of 2 grams obtained in Example 6,photo acid generator (triphenylsulfoniumnonaphlate) of 0.04 grams,2,6-diisopropylaniline of 0.004 grams, andpropyleneglycolmonomethyletheracetate of 11.5 grams was filtered with a0.2-μm Teflon filter to thereby prepare resist composition.

[0235] An organic antireflection film having a thickness of 0.1micrometer was formed on a 8-inch silicon substrate. The above-mentionedresist composition was coated onto the substrate by a spin-coatingprocess, and then, was baked on a hot plate for a minute at 130 degreescentigrade. Thus, there was formed a thin resist film having a thicknessof 0.4 micrometers.

[0236] Then, the resist film was exposed to light by means of an ArFstepper apparatus (available from Nikon, NA=0.6).

[0237] Immediately after the exposure, the resist film was baked on ahot plate for 60 seconds at 135 degrees centigrade. Then, the resistfilm was emerged in aqueous solution of 2.38% (CH₃)₄NOH(TMAH) for 60seconds at a liquid temperature of 23 degrees centigrade fordevelopment. Then, the resist film was rinsed with pure water for 60seconds.

[0238] As a result, only a portion of the resist film having beenexposed to light was removed by the developing agent, and thus, therewas obtained a positive pattern. A resolution was measured by SEMobservation with respect to the obtained pattern. Sensitivity wasdetermined as a light volume at which the obtained L/S (line and space)pattern could be resolved at 1:1.

[0239] Patterning was estimated in the same way as mentioned above withrespect to resist composition composed of acrylic polymer obtained inExample 11 and resist composition composed of norbornane polymerobtained in Example 15.

[0240] The estimate results are shown in Table 3. TABLE 3 ResolutionDensity (μmL/S) (mJ/cm²) Resist including resin of Example 6 0.13 21Resist including resin of Example 11 0.13 18 Resist including resin ofExample 15 0.15 28

[0241] It was proved that a photoresist material including the polymerin accordance with the present invention (Examples 6, 11 and 15) hadhigh sensitivity and resolution.

[0242] [Estimate to Adhesion to a Substrate]

[0243] A substrate on which a photoresist was patterned was observed bymeans of SEM. As a result, it was observed that the pattern was notpeeled off the substrate, and hence, it was found out that a photoresistmaterial including the polymer in accordance with the present invention(Examples 6, 11 and 15) had sufficient adhesion to a substrate.

Example 17

[0244] Monomer obtained in Example 3 was polymerized in ring openingmetathesis. Hydrogen was added to the resultant resin through palladiumcatalyst. Thus, there was obtained acrylic polymer comprised of astructural unit by 100 mol % which is defined in accordance with thegeneral formula (III) wherein R¹ represents a hydrogen atom, R² and R³each represents a methyl group, X represents —CH₂—, Z represents ahydrogen atom, and n is equal to one (1).

Example 18

[0245] Resist composed of polymer obtained in Examples 7 to 10 and 12 to14 has sufficient resistance to etching, transparency, sensitivity,resolution and adhesion to a substrate.

INDUSTRIAL APPLICABILITY

[0246] The resin having a repeated structural unit including a bridgedalicyclic γ-lactone structure in accordance with the present inventionpresents chemically-amplified resist composition which is excellent inresistance to etching, transparency to light having a wavelength of 220nm or smaller, resolution, and adhesion to a substrate. Furthermore, thechemically-amplified resist composition makes it possible to form aminute pattern necessary for fabrication of a semiconductor device.

1-12. (cancelled).
 13. A (metha)acrylate derivative having a bridgedalicyclic γ-lactone structure defined in the general formula (I):

wherein R¹ represents one of a hydrogen atom and a methyl group, R² andR³ each represents one of a hydrogen atom and an alkyl group having acarbon number in the range of 1 to 6 both inclusive, or R² and R³ linkeach other, and each represents an alkylene group having a carbon numberin the range of 1 to 6 both inclusive and cooperating with a carbon atomto which R² and R³ link to define a ring, X represents one of —CH2- and—O—, Z represents one of a hydrogen atom and a methyl group, and nrepresents one of 0 and 1 wherein when n represents 0 and X represents—CH2-, R² and R³ each represents a carbon number in the range of 1 to 6both inclusive.
 14. An unsaturated monomer having a bridged alicyclicγ-lactone structure defined in the general formula (II):

wherein R⁴ and R⁵ each represents one of a hydrogen atom and an alkylgroup having a carbon number in the range of 1 to 6 both inclusive, orR⁴ and R⁵ link each other, and each represents an alkylene group havinga carbon number in the range of 1 to 6 both inclusive and cooperatingwith a carbon atom to which R⁴ and R⁵ link to define a ring.
 15. Apolymer resulted from (co)polymerizing a monomer composition containingat least one of (metha)acrylate derivative and unsaturated monomer,wherein said (metha)acrylate derivative has a bridged alicyclicγ-lactone structure defined in the general formula (I):

wherein R¹ represents one of a hydrogen atom and a methyl group, R² andR³ each represents one of a hydrogen atom and an alkyl group having acarbon number in the range of 1 to 6 both inclusive, or R² and R³ linkeach other, and each represents an alkylene group having a carbon numberin the range of 1 to 6 both inclusive and cooperating with a carbon atomto which R² and R³ link to define a ring, X represents one of —CH2- and—O—, Z represents one of a hydrogen atom and a methyl group, and nrepresents one of 0 and 1 wherein when n represents 0 and X represents—CH2-, R² and R³ each represents a carbon number in the range of 1 to 6both inclusive, said unsaturated monomer has a bridged alicyclicγ-lactone structure defined in the general formula (II):

wherein R⁴ and R⁵ each represents one of a hydrogen atom and an alkylgroup having a carbon number in the range of 1 to 6 both inclusive, orR⁴ and R⁵ link each other, and each represents an alkylene group havinga carbon number in the range of 1 to 6 both inclusive and cooperatingwith a carbon atom to which R⁴ and R⁵ link to define a ring.
 16. Thepolymer as set forth in claim 15, wherein a weight-average molecularweight of said polymer is in the range of 2,000 to 200,000 bothinclusive.
 17. A polymer including at least one of a repeated structuralunit having a bridged alicyclic γ-lactone structure defined in thegeneral formula (III), a repeated structural unit having a bridgedalicyclic γ-lactone structure defined in the general formula (IV), and arepeated structural unit having a bridged alicyclic γ-lactone structuredefined in the general formula (V):

wherein R¹ represents one of a hydrogen atom and a methyl group, R² andR³ each represents one of a hydrogen atom and an alkyl group having acarbon number in the range of 1 to 6 both inclusive, or R² and R³ linkeach other, and each represents an alkylene group having a carbon numberin the range of 1 to 6 both inclusive and cooperating with a carbon atomto which R² and R³ link to define a ring, X represents one of —CH2- and—O—, Z represents one of a hydrogen atom and a methyl group, and nrepresents one of 0 and 1 wherein when n represents 0 and X represents—CH2-, R² and R³ each represents a carbon number in the range of 1 to 6both inclusive,

wherein R⁴ and R⁵ each represents one of a hydrogen atom and an alkylgroup having a carbon number in the range of 1 to 6 both inclusive, orR⁴ and R⁵ link each other, and each represents an alkylene group havinga carbon number in the range of 1 to 6 both inclusive and cooperatingwith a carbon atom to which R⁴ and R⁵ link to define a ring,

wherein R⁴ and R⁵ each represents one of a hydrogen atom and an alkylgroup having a carbon number in the range of 1 to 6 both inclusive, orR⁴ and R⁵ link each other, and each represents an alkylene group havinga carbon number in the range of 1 to 6 both inclusive and cooperatingwith a carbon atom to which R⁴ and R⁵ link to define a ring.
 18. Thepolymer as set forth in claim 17, wherein a content ratio of saidrepeated structural unit defined in the general formula (III), (IV) or(V) to said polymer in its entirety is in the range of 5 to 90 mol %both inclusive.
 19. The polymer as set forth in claim 17, wherein aweight-average molecular weight of said polymer is in the range of 2,000to 200,000 both inclusive.
 20. A chemically-amplified resist compositioncontaining a polymer, wherein said polymer is resulted from(co)polymerizing a monomer composition containing at least one of(metha)acrylate derivative and unsaturated monomer, wherein said(metha)acrylate derivative has a bridged alicyclic γ-lactone structuredefined in the general formula (I):

wherein R¹ represents one of a hydrogen atom and a methyl group, R² andR³ each represents one of a hydrogen atom and an alkyl group having acarbon number in the range of 1 to 6 both inclusive, or R² and R³ linkeach other, and each represents an alkylene group having a carbon numberin the range of 1 to 6 both inclusive and cooperating with a carbon atomto which R² and R³ link to define a ring, X represents one of —CH2- and—O—, Z represents one of a hydrogen atom and a methyl group, and nrepresents one of 0 and 1 wherein when n represents 0 and X represents—CH2- , R² and R³ each represents a carbon number in the range of 1 to 6both inclusive, said unsaturated monomer has a bridged alicyclicγ-lactone structure defined in the general formula (II):

wherein R⁴ and R⁵ each represents one of a hydrogen atom and an alkylgroup having a carbon number in the range of 1 to 6 both inclusive, orR⁴ and R⁵ link each other, and each represents an alkylene group havinga carbon number in the range of 1 to 6 both inclusive and cooperatingwith a carbon atom to which R⁴ and R⁵ link to define a ring.
 21. Thechemically-amplified resist composition as set forth in claim 20,further comprising a photo acid generator which generates acid whenexposed to light.
 22. The chemically-amplified resist composition as setforth in claim 21, wherein a content of said photo acid generator is inthe range of 0.2 to 30 mass % both inclusive relative to a total contentof said polymer and said photo acid generator.
 23. Thechemically-amplified resist composition as set forth in claim 21,wherein said photo acid generator generates acid when light having awavelength in the range of 180 to 220 nanometers both inclusive isirradiated thereto.
 24. A chemically-amplified resist compositioncontaining a polymer, wherein said polymer includes at least one of arepeated structural unit having a bridged alicyclic γ-lactone structuredefined in the general formula (III), a repeated structural unit havinga bridged alicyclic γ-lactone structure defined in the general formula(IV), and a repeated structural unit having a bridged alicyclicγ-lactone structure defined in the general formula (V):

wherein R¹ represents one of a hydrogen atom and a methyl group, R² andR³ each represents one of a hydrogen atom and an alkyl group having acarbon number in the range of 1 to 6 both inclusive, or R² and R³ linkeach other, and each represents an alkylene group having a carbon numberin the range of 1 to 6 both inclusive and cooperating with a carbon atomto which R² and R³ link to define a ring, X represents one of —CH2- and—O—, Z represents one of a hydrogen atom and a methyl group, and nrepresents one of 0 and 1 wherein when n represents 0 and X represents—CH2-, R² and R³ each represents a carbon number in the range of 1 to 6both inclusive,

wherein R⁴ and R⁵ each represents one of a hydrogen atom and an alkylgroup having a carbon number in the range of 1 to 6 both inclusive, orR⁴ and R⁵ link each other, and each represents an alkylene group havinga carbon number in the range of 1 to 6 both inclusive and cooperatingwith a carbon atom to which R⁴ and R⁵ link to define a ring,

wherein R⁴ and R⁵ each represents one of a hydrogen atom and an alkylgroup having a carbon number in the range of 1 to 6 both inclusive, orR⁴ and R⁵ link each other, and each represents an alkylene group havinga carbon number in the range of 1 to 6 both inclusive and cooperatingwith a carbon atom to which R⁴ and R⁵ link to define a ring.
 25. Thechemically-amplified resist composition as set forth in claim 24,further comprising a photo acid generator which generates acid whenexposed to light.
 26. The chemically-amplified resist composition as setforth in claim 25, wherein a content of said photo acid generator is inthe range of 0.2 to 30 mass % both inclusive relative to a total contentof said polymer and said photo acid generator.
 27. Thechemically-amplified resist composition as set forth in claim 25,wherein said photo acid generator generates acid when light having awavelength in the range of 180 to 220 nanometers both inclusive isirradiated thereto.
 28. A method of forming a pattern, comprising atleast the steps, in sequence, of: coating a chemically-amplified resistcomposition defined in claim 20 onto a substrate; baking saidchemically-amplified resist composition; exposing saidchemically-amplified resist composition to light having a wavelength inthe range of 180 to 220 nanometers both inclusive; baking saidchemically-amplified resist composition; and developing saidchemically-amplified resist composition.
 29. The method as set forth inclaim 28, wherein said light is comprised of ArF excimer laser beams.30. A method of forming a pattern, comprising at least the steps, insequence, of: coating a chemically-amplified resist composition definedin claim 24 onto a substrate; baking said chemically-amplified resistcomposition; exposing said chemically-amplified resist composition tolight having a wavelength in the range of 180 to 220 nanometers bothinclusive; baking said chemically-amplified resist composition; anddeveloping said chemically-amplified resist composition.
 31. The methodas set forth in claim 30, wherein said light is comprised of ArF excimerlaser beams.